1. Field of the Invention
The present invention relates to transducers and more specifically to transducers that use a magnet assembly, such as speaker systems.
2. Description of the Related Art
A speaker is a type of electro-acoustic transducer, which is a device that converts an electrical audio signal into sound corresponding to the signal. Speakers were invented during the development of telephone systems in the late 1800s. However, it was electronic amplification, initially by way of vacuum tube technology beginning around 1912 that began to make speaker systems practical. The amplified speaker systems were used in radios, phonographs, public address systems and theatre sound systems for talking motion pictures starting in the 1920s.
The dynamic speaker, which is widely used today, was invented in 1925 by Edward Kellogg and Chester Rice. A principle of the dynamic speaker is when an electrical audio signal input is applied through a voice coil, which is a coil of wire suspended in a circular gap between the poles of a permanent magnet, the coil is forced to move rapidly back and forth due to Faraday's law of induction. The movement causes a diaphragm, which is generally conically shaped, and is attached to the coil to move back and forth, thereby inducing movement of the air to create sound waves.
Speakers are typically housed in an enclosure and if high quality sound is required, multiple speakers may be mounted in the same enclosure, with each reproducing part of the audio frequency range. In this arrangement the speakers are individually referred to as “drivers” and the entire enclosure is referred to as a speaker or a loudspeaker. Small speakers are found in various devices such as radio and TV receivers, and a host of other devices including phones and computer systems.
A problem with electrical transducers in general and speakers in particular is that speaker efficiency, which is defined as the sound power output divided by the electrical power input, is only about 1%. So very little of the electrical energy sent by an amplifier to a typical speaker is converted to acoustic energy. The remainder of the energy is converted to heat, mostly in the voice coil and magnet assembly. The main reason for this is the difficulty of achieving a proper impedance matching between the acoustic impedance of the drive unit and the air it radiates into. The efficiency of speaker drivers varies with frequency as well as the magnetic intensity available to interact with the voice coil.
What is needed in the art is an electro-acoustic transducer that can be used with speakers or other devices which has increased effectiveness that will allow more compact designs and will result in more efficient production of sound or movement.